In typical digital cameras, white balance (hereinafter may be transcribed as WB) control is performed based on a light source type determined from a spectrum distribution obtained by analyzing reflected light thrown back from a subject. In other words, digital cameras vary white balance control values depending on light source types determined to achieve color reproduction independent from light source color. Since the balance of signal levels outputted from imaging devices such as CCDs vary according to drive methods, compensation is performed depending on spectral sensitivity during the analysis of reflected light. For instance, known CCD drive methods include field readout and frame readout. Field readout is a drive method that adds and reads out each two pixels in a vertical direction of the CCD, and is typically used for shooting moving images. On the other hand, frame readout is a method that reads out each pixel in a vertical direction of the CCD without adding each two pixels, and is typically used for shooting still images.
In addition, digital video cameras capable of shooting still images at a desired time during moving image shooting are known. A technique for reducing and preventing variances in the color reproducibility of images attributable to the differences in the CCD drive methods when shooting still images during shooting of moving images with digital video cameras of this type is disclosed in Japanese Patent Laid-Open No. 2001-069409. According to Japanese Patent Laid-Open No. 2001-069409, a sensitivity difference between the CCDs of such driving methods is memorized in advance in order to absorb the difference in sensitivities of CCDs due to differences in drive methods. Using a signal obtained by the drive method for moving image shooting, and the memorized sensitivity difference, an aperture to be applied to the drive method for still image shooting is determined. According to Japanese Patent Laid-Open No. 2001-069409, white balance coefficients are appropriately set in response to switching of driving methods.
Furthermore, Japanese Patent Laid-Open No. 2004-201282 describes a control for a digital camera that temporarily suspends driving of the CCD for moving image shooting, switches to driving for still image shooting to shoot a still image, and thereafter returns to driving for moving image shooting in order to shoot still images while shooting moving images. Japanese Patent Laid-Open No. 2004-201282 further describes generating an alternate frame corresponding to a moving image frame that is dropped due to shooting still images during moving image shooting.
Typically, as described above, when shooting still images during shooting moving images with digital video cameras, CCD drive modes differ between moving image shooting and still image shooting. Since such variations in drive modes result in variation in CCD spectral sensitivities, it is necessary to change development processing parameters according to drive mode. For instance, processing such as switching white balance coefficients depending on drive modes is necessary. However, Japanese Patent Laid-Open No. 2004-201282 does not consider varying development processing depending on drive modes. In Japanese Patent Laid-Open No. 2004-201282, since the last frame taken in moving image shooting-mode immediately prior to shooting still images is used as an alternate frame, continuity of image color is maintained through moving image shooting. However, since still images are also developed using parameters for moving images, the difference in spectral sensitivities of still images taken during moving image shooting cannot be compensated. Therefore, it is possible that the resulting still images are not totally satisfactory. Also, while Japanese Patent Laid-Open No. 2001-069409 describes changing parameters for development processing when shooting still images during moving image shooting, alternate frames are not mentioned.
Moreover, in Japanese Patent Laid-Open No. 2004-201282, the use of the moving image frame immediately prior to the shooting of a still image means that the motion of the moving image is stopped, and may result in apparent unnaturalness. Therefore, reduction of the still image may be considered as a method for generating alternate frames. This method improves the unnaturalness of the motion in the moving images, as compared to using the moving image frame immediately prior to the shooting of the still image. Consequently, it is possible to consider applying Japanese Patent Laid-Open No. 2004-201282 to a configuration that generates alternate frames by reducing still images. However, in this case, CCD frame readout is performed upon shooting still images during moving image shooting. When reducing still images obtained in this way and using them as alternate frames, since moving image shooting is performed by reading out single fields, a problem arises where color continuity is not maintained between the period of shooting still images during moving image shooting, and the periods before and after that period.
As seen, conventional digital video cameras are incapable of giving satisfactory color to both still images obtained by still image shooting during moving image shooting, and alternate frames to be inserted in the moving image during such still image shooting.